There is a growing interest in the use of lasers for general dental, medical or surgical applications and it is generally believed that longer wave length laser beams, such as emitted from the carbon monoxide and carbon dioxide lasers at five and ten micrometers respectively, are preferred to the shorter wavelengths that are derived from the Nd: YAG and Argon ion lasers at 1.06 micrometers and 0.5 micrometers respectively. This preference with respect to surgical useage is due to the fact that the longer wave length radiation is highly absorbed by human tissues so that the illuminated zone is well defined and the extent of damage in cauterization is limited in depth to a single or few layers of cells. Although endoscopes for the purpose of observation of the interior of the human body have been well known for many years, there has heretofore been no practical way of delivering a CO or CO.sub.2 laser beam to the inside of the body.
The development of a hollow metallic waveguide that can guide the CO.sub.2 laser output has been reported by E. Garmire et al of the University of Southern California in Applied Physics Letters, Vol. 29 pp. 254-256, (1976). This guide, however, is considered excessively large in cross-section for most endoscopic treatment or surgical procedures.
There has recently been developed a new fiber optic waveguide suitable for transmitting infrared radiation which comprises a waveguide core formed from an extruded crystalline material which is a halide of a metal. This infrared transmitting fiber optical waveguide forms the subject matter of U.S. patent application, Ser. No. 800,149, filed May 24, 1977, on behalf of Douglas A. Pinnow et al entitled "Infrared Transmitting Fiber Optical Waveguide Extruded From Halides" and assigned to the assignee of the present application. The present invention pertains to means for safely and effectively using this new waveguide in a an instrument for applying laser energy to a selected part of the body.